The Palestinian president on Sunday called the Holocaust “the most heinous crime” of modern history, voicing a rare acknowledgment of Jewish suffering shortly before Israel held its annual memorial for victims of the Nazi genocide.

President Mahmoud Abbas’ announcement appeared to be aimed at reaching out to Israeli public opinion at a time of deep crisis in U.S.-backed peace efforts. Israelis frequently claim the Palestinians are not sincere about wanting peace.

While Israel’s national Holocaust memorial said Abbas’ comments may be a step in the right direction, Israeli Prime Minister Benjamin Netanyahu brushed them aside.

He said the Abbas’ renewed attempts to reconcile with the Islamic militant movement Hamas raised doubts about the Palestinian leader’s intentions. Hamas, a movement sworn to Israel’s destruction, has questioned the Holocaust and blocked the subject from being taught in schools in the Gaza Strip.

“President Abbas can’t have it both ways. He can’t say the Holocaust was terrible, but at the same time embrace those who deny the Holocaust and seek to perpetrate another destruction of the Jewish people,” Netanyahu told CNN.

For Abbas, however, conciliatory language marked a breakthrough of sorts.

Denials or attempts to minimize the Holocaust, which saw the systematic killing of 6 million Jews by Nazi Germany in World War II, are widespread in the Arab world.

Many Palestinians fear that if they acknowledge the Holocaust, they will diminish their own claims based on years of suffering, including their uprooting during Israel’s 1948 creation and decades under Israeli occupation.

Abbas himself has been accused of minimizing the scope of the Holocaust in a doctoral dissertation in the 1970s, though in recent years he’s edged toward acknowledging Jewish suffering.

Abbas’ statement came as the latest U.S. attempt to broker an Israeli-Palestinian peace deal was on the verge of collapse. He urged Israel not to walk away.